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Test-Retest Discrepancy in Vocabulary Scores on WPPSI-III
By Inderbir Kaur Sandhu, Ph.D
Q: I'm not quite sure if I have a question. I guess I want to know if there is more I should look into. My son has taken the WPPSI-III twice. The first time was for entry into a private school for gifted kids. We had been out of town the day before, so he was not in any condition to take the test. He was tired and was more interested in what was going on in the school than taking the test so he refused to finish the test.
Since he has continued to have problems at day care (no participation, trouble with transitions, ADHD diagnosis, mild SPD) We decided to get him evaluated for services through the public school. He attended a classroom for 3 hours a day over a week. There he was evaluated by various professionals. The school psychologist gave him the WPPSI-III. In the classroom those three hours he did great. He participated, completed several step projects and was eager to answer questions. They did not see any of the issues we see at home and at day care everyday. It does seem that he does best when he has something to focus on and feels he is being challenged (we told him he was at kindergarten practice). Outside of that classroom, that week, he fell apart at school and at home.
My concern is that there is a huge difference in his vocabulary scores between the first test and the second test. I'm not too concerned with the other scores. I'm not even concerned about the overall score. He seems to not be a happy student and with 12 years of school ahead of him I want him to be in the right environment. Can the difference in score be explained by the age, different tester? The scores are listed below. I tried to list in table format. I hope it's readable. Thanks!
First WPPSI-III at age 4yrs 2wks
Verbal Scaled Scores Percentile
Information 15 95
Vocabulary 19 99.9
Performance
Block Design 12 75
Matrix Reasoning 16 98
Pictures Concepts 15 95
Processing
Coding 11 63
(Symbol Search) 10 50
Verbal IQ 143 prorated (he refused to finish the test)
Performance IQ 127
Processing Speed 102
Full Scale IQ 135
Second WPPSI-III at age 5yrs 5wks
Verbal Raw Score Scaled Scores Percentile
Information 26 12 75
Vocabulary 23 12 75
Word Reasoning 18 11 63
Performance
Block Design 34 17 99
Matrix Reasoning 19 14 91
Pictures Concepts 17 13 84
Processing
Coding 21 13 84
(Symbol Search) 32 13 84
Verbal IQ 108
Performance IQ 129
Processing Speed 116
Full Scale IQ 122
A: There is indeed a discrepancy vocabulary scores between the periods the test was taken. There are two subtests; performance and verbal. The verbal subtests consists of Information (child is required to either point to a picture or verbally answer brief oral questions about commonplace objects and events); Comprehension (child verbally responds to questions about consequences of events); Vocabulary (child names pictured items and provides verbal definition of words), and Similarities (child completes a sentence that contains a verbal analogy).
The WPPSI III included additions from its previous WPPSI-R, which included Picture Naming (child names pictures that are displayed singularly in the stimulus booklet); Receptive Vocabulary (child looks at a group of four pictures and points to the one that the examiner describes aloud); Word Reasoning (child is read an increasingly specific series of one to three clues and identifies the common object or concept being described. Optional subtests are Receptive Vocabulary and Picture Naming.
The retest a year later may have lowered his verbal IQ. In essence, the WPPSI-III is a fairly stable instrument with average test-retest coefficients. I am not sure as to why his vocabulary scores have dropped though the scores are not that low. In fact, he should have been given a subtest if there was a concern. Perhaps, the tester did not see anything amiss. Do you see a problem with his vocabulary? You also mentioned that he appears not to be a happy student; this is rather disturbing at such a young age. The difference in scores may not be due to age as it is a scaled score and normed with age. Unless his vocabulary has not improved much after a year and that does not seem very possible (of course also, unless he has a learning disability that was not attended to and worsened over time). An experienced tester would be able to test much better and gauge behavioural cues while testing. You may want to speak to the tester to determine his behaviour at the point of testing.
What I see here is a child that needs proper behavioural intervention and an individualised learning programme. See a child psychologist who may be able to help you further with his behaviour and learning. He may need further testing to rule out other learning and health concerns. My very best to you.
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